Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monoethyl Ether–n-Alcohol Mixtures at 25°C

We have measured excess molar volumes V^E _m of binary mixtures of triethylene glycol monoethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol over the full range of compositions at 25°C. The measurements were carried out with a continuous-dilution dilatometer. The excess molar volumes V^E _m are negative over the entire range of composition for the systems triethylene glycol monoethyl ether + methanol, + ethanol, and + 1-propanol and positive for the remaining systems, triethylene glycol monoethyl ether + 1-pentanol, and + 1-hexanol. The excess V^E _m increases in the positive direction with increasing chain length of the n-alcohol. The measured excess volumes have been compared to our previous published data with an effort to assess the effects of replacing methyl by ethyl groups and of inserting oxyethylene groups. The results have been used to estimate the excess partial molar volumes V^E _m,i of the components. The behavior of V^E _m and V^E _m,i with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monomethyl Ether–n-Alcohol Mixtures at 25°C

The excess molar volumes V ^E have been measured for binary mixtures of triethylene glycol monomethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol as a function of composition using a continuous–dilution dilatometer at 25°C at atmosphere pressure. V ^E are negative over the entire range of composition for the systems triethylene glycol monomethyl ether + methanol, + ethanol, and + 1-propanol, and positive for the remaining systems, containing 1-pentanol and + 1-hexanol. V ^E increases in a positive direction with increasing carbon chain length of the n-alcohol. The excess partial molar volumes V _i ^E of the components were evaluated from the V ^E results. The behavior of V ^E and V _i ^E with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Apparent Molar Volumes and Viscosities of Dl-α-Alanine in Water-Ethanol Mixtures

Abstract

In this work we present a systematic study of the apparent molar volumes and the viscosities of DL-α-alanine in aqueous ethanol solutions at 25,00°C. The molar fractions of ethanol for the solvent mixtures were selected taking into account that thermodynamic properties such as partial molar volumes and heat capacities of these mixtures show a transition concentration around X _et = 0,1 at which its behavior suffers a deep change. Besides, this ethanol concentration is near to that required to produce 50% of protein denaturation.

The results were used to evaluate the limiting partial molar volume V0 of the solute the volume changes associated with its transfer from water to aqueous ethanol solutions and the viscosity B coefficients of DL-α-alanine. The values obtained for the transference molar volumes and the viscosity B coefficients of alanine in the aqueous mixtures show a minimum at X _et = 0,1000. The results are discussed in terms of changes in the solvent structure (Ref. [1])     

Partial Molar Volumes of Alkylated Uracils--Insight into the Solvation Shell? Part II

The solute–solvent interactions in aqueous solutions of alkylated uracils are discussed. The partial molar volume data are interpreted using a new model of interaction of the solute molecule with the solvent. The model is based on the assumption that the density of solvent in the hydration shell depends on the structure and polarity of the solute molecule. The relation among molecular volume, partial molar volume, and volume of the solvation shell is expressed by parameter, which is defined as the relative density of the solvation shell. It is found that in compounds with the same number of CH₂- groups, the values depend on substitution on the C or N atoms of the uracil skeleton. The values also depend to some extent, on screening of the oxygen atoms by methylation of the neighboring atoms of the uracil ring. A correlation is presented between the relative density of solvation shell and polarity (defined as the ratio of the surface of polar groups and atoms exposed to the solvent to the total accessible molecular surface of the molecule) for the compounds studied. It was demonstrated that of the various solute–solvent interactions the dominant role is played by polar interactions.     

Apparent Molar Volumes of Multicharged Cations in Dimethyl Sulfoxide Solutions at 25°C

Densities for DMSO solutions of iron(III), aluminium(III), beryllium(II) and magnesium(II) perchlorates and silver nitrate are reported. Densities for DMSO solutions of tetraethylammonium perchlorate and nitrate and tetrabutylammonium perchlorate and tetraphenylborate are also presented. The partial molar volumes of the DMSO-solvated cations are derived and discussed in terms of variation with the charge number.     

Excess Molar Volumes of Binary Mixtures of Hexanol and Polyethers at 25°C

Excess molar volumes V_m^E at 25°C and atmospheric pressure over the entire composition range for binary mixtures of 1-hexanol with n-polyethers: 2,5-dioxahexane, 3,6-dioxaoctane, 2,5,8-trioxanonane, 3,6,9-trioxaundecane, 5,8,11-trioxapentadecane, 2,5,8,11-tetraoxadodecane, and 2,5,8,11,14-pentaoxapentadecane are reported from densities measured with a vibrating-tube densimeter. Systems containing 2,5-dioxahexane, 2,5,8-trioxanonane, 2,5,8,11-tetraoxadodecane or 2,5,8,11,14-pentaoxapentadecane are characterized by V_m^E > 0, probably due to predominant positive contributions to V_m^E from the disruption of H bonds of 1-hexanol and to physical interactions. In contrast, mixtures with 3,6-dioxaoctane, 3,6,9-trioxaundecane, and 5,8,11-trioxapentadecane are characterized by V_m^E < 0, indicating that the negative contribution to V_m^E from interstitial accommodation is more important.     

Determination of Partial Molar Volumes of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide

The use of supercritical fluids (SCFs) as solvents has been attracting widespread interest in the research and commercial applications. The study of partial molar volumes of solutes at infinite dilution in the near-critical region is of considerable fundamental importance, as these data reflects the interactions occurring between the solute and the solvent. Experimental measurements of partial molar volumes may be divided into two categories: direct and indirect methods. The direct methods…     

Deptermination of Partial Molar Volumes of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide

The use of supercritical-fluid shromatogrphy for determining partial molar volumes of ethyl esters of cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and cis-4,7,10,13,16,19-docosa-hexaenoic acid(DHA) in supercritical carbon dioxide is presented and discussed. Partial molar volumes of EPA and DHA esters are obtained from the variation of the retention properties with the density of mobile phase at 313.15K,323.15K,333.15K and in the pressure range from 9 MPa to 21 MPa.     

Molecular Interactions in 1-Ethyl-3-Methylimidazolim Tetrafluoroborate + Amide Mixtures: Excess Molar Volumes, Excess Isentropic Compressibilities and Excess Molar Enthalpies

The densities, ρ ₁₂, and speeds of sound, u ₁₂, of 1-ethyl-3-methylimidazolium tetrafluoroborate (1) + N-methylformamide or N,N-dimethylformamide (2) binary mixtures at (293.15. 298.15. 303.15, 308.15 K), and excess molar enthalpies, $ H_{12}^{\text{E}} $ H 12 E , of the same mixtures at 298.15 K have been measured over the entire mole fraction range using a density and sound analyzer (Anton Paar DSA-5000) and a 2-drop microcalorimeter, respectively. Excess molar volume, $ V_{12}^{\text{E}} $ V 12 E , and excess isentropic compressibility, $ \left( {\kappa_{S}^{\text{E}} } \right)_{12} $ ( κ S E ) 12 , values have been calculated by utilizing the measured density and speed of sound data. The observed data have been analyzed in terms of: (i) Graph theory and (ii) the Prigogine–Flory–Patterson theory. Analysis of the $ V_{12}^{\text{E}} $ V 12 E data in terms of Graph theory suggest that: (i) in pure 1-ethyl-3-methylimidazolium tetrafluoroborate, the tetrafluoroborate anion is positioned over the imidazoliun ring and there are interactions between the hydrogen atom of (C–H{edge}) and proton of the –CH₃ group (imidazolium ring) with fluorine atoms of tetrafluoroborate anion, and (ii) (1 + 2) mixtures are characterized by ion–dipole interactions to form a 1:1 molecular complex. Further, the $ V_{12}^{\text{E}} $ V 12 E , $ H_{12}^{\text{E}} $ H 12 E and $ \left( {\kappa_{S}^{\text{E}} } \right)_{12} $ ( κ S E ) 12 values determined from Graph theory compare well with their measured experimental data.     

Partial Molar Volumes of Hydrophobic Compounds—Insight into the Solvation Shell? Part I

A simple model for the interaction of the solute with the solvent is presented. The relation between the molecular volume, partial molar volume, and the volume of the solvation shell of the compound studied is expressed by the parameter, defined as the relative density of the solvation shell. The values of are calculated for many organic compounds in aqueous solutions. It is stated that in a given series of compounds, depends strongly on the number of CH₂ groups in the compound studied. The correlation of and the polarity (defined as the ratio of the surface area of polar groups and atoms exposed to the total molecular surface area of the molecule studied) was found.     

Excess Molar Volumes, Excess Molar Enthalpies, and Excess Isentropic Compressibilities of Binary Mixtures Containing N-Methyl-2-Pyrrolidone and Isomeric Xylenes at 308.15?K

Excess molar volumes, excess molar enthalpies and speeds of sound of 1-methyl pyrrolidin-2-one?+?o- or m- or p-xylene binary mixtures have been measured over the entire composition range at 308.15?K. The speed of sound data were used to determine the excess isentropic compressibilities. It is observed that while the values of the excess molar enthalpies for the investigated mixtures are positive, the values of the excess molar volumes and excess isentropic compressibilities are negative over the entire composition range. The measured thermodynamic data have been analyzed in terms of Graph, Prigogine?CFlory?CPatterson, and the Sanchez and Lacombe theories. It is observed that Graph theory correctly predicts the signs and magnitudes of the excess molar volumes, excess molar enthalpies, and excess isentropic compressibilities of the studied mixtures. However, the excess molar volumes, excess molar enthalpies and excess isentropic compressibilities predicted by Prigogine?CFlory?CPatterson and Sanchez and Lacombe theories are of same sign.     

Excess Molar Volumes of Ternary Mixtures of a Cyclic Ether with Aromatic Hydrocarbons at 308.15 K

Excess molar volumes, V_ijk^EV_{ijk}^{E}, are reported for ternary mixtures of tetrahydropyran (i)+benzene (j)+toluene or o- or p-xylenes (k) and tetrahydropyran (i)+toluene (j)+o- or p-xylenes (k) as a function of composition at 308.15 K. These V_ijk^EV_{ijk}^{E} values have been fitted to the Redlich–Kister equation to predict ternary adjustable parameters and standard deviations. The measured V_ijk^EV_{ijk}^{E} data have been analyzed in terms of Graph theory (which involves the topology of the constituents of mixtures). It has been observed that V_ijk^EV_{ijk}^{E} values predicted by Graph theory compare well with their corresponding experimental values.     

Limiting Partial Molar Excess Heat Capacities and Volumes of Selected Organic Compounds in Water at 25°C

Well-known Picker flow microcalorimeters for the differential measurements of volumetric heat capacities have been employed in conjunction with vibrating tube densimeters to determine the molar heat capacity, volume, and the apparent properties in dilute aqueous solutions for 17 organic solutes of moderate hydrophobicity. The dependence on concentration of the apparent properties allowed the limiting partial molar quantities at infinite dilution to be extrapolated and the limiting partial molar excess quantities to be evaluated. Comparison with available literature data shows good agreement. The application of group contribution rules to the limiting partial properties has been tested using the original method and parameters proposed by Cabani et al. The predicted values of the partial molar volumes are in fair agreement with the present data except for some less common solutes. With partial molar heat capacities, the agreement is less satisfactory. To improve the performance of the method, missing parameters for some types of monofunctional and bifunctional molecules have been evaluated.     

Partial Molar Volumes of Transfer of Some Amino Acids from Water to Aqueous Glycerol Solutions at 25°C

Apparent molar volumes of glycine, DL--alanine, L-valine, L-leucine, and L-phenylalanine in 0.5, 1.0, 2.0, 3.5, and 5.0 m _B (mol-kg^–1) aqueous solutions of glycerol have been obtained from solution densities at 25°C using precise vibrating-tube digital densimeter. The estimated partial molar volumes at infinite dilution V ^o ₂ have been used to obtain the corresponding transfer volumes _tr V ₂ ^o from water to different glycerol–water mixtures. The transfer volumes are positive for glycine and DL--alanine, and both positive and negative for the other amino acids over the concentration range studied. Interaction coefficients have been obtained from McMillan–Mayer approach and the data have been interpreted in terms of solute–cosolute interactions.     

Apparent Molar Volumes of Aqueous Solutions of Magnesium Tetraborate from 283.15 to 363.15 K and 0.1 MPa

Densities for aqueous solutions of magnesium tetraborate MgB₄O₇(aq) at the molalities of (0.00556–0.03341) mol·kg^?1 were measured with an Anton Paar Digital vibrating-tube densimeter at temperature intervals of 5 K from 283.15 to 363.15 K and 0.1 MPa. Apparent molar volumes were obtained based on the experimental density data, and the 3D diagrams of the apparent molar volume (V _? ) of MgB₄O₇(aq) against temperature (T) and molality (m) were plotted. On the basis of the Vogel–Tamman–Fulcher equation, the coefficients of the correlation equation for densities of MgB₄O₇(aq) against temperature and molality were parameterized. According to the Pitzer ion-interaction model of the apparent molar volume, the temperature correlation equations of Pitzer single-salt parameters F(i,p,T)?=?a₀?+?a₁?×?T?+?a₂?×?T ²?+?a₃/T?+?a₄?×?ln(T)?+?a₅?×?T ³ (where T is temperature in Kelvin, a _i are model parameters) for MgB₄O₇ were obtained for the first time.     

Densities and Partial Molar Volumes of Some Amino Acids and Diglycine in Aqueous n-Propanol Solutions at 25°C

Apparent molar volumes, V , of glycine, DL--alanine, DL--amino-n-butyric acid, L-valine, L-leucine, and diglycine in water and in 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 m _B [molality of n-propanol in water (mol-kg^–1)] aqueous solutions of n-propanol have been obtained from densities of their solutions at 25 °C measured by using a precise vibrating-tube digital densimeter. The calculated partial molar volumes of amino acids and diglycine at infinite dilution, V _2,m ^o , have been used to obtain the corresponding transfer volumes, _tr V _2,m ^o , from water to different n-propanol–water mixtures. _tr V _2,m ^o values are positive for glycine, DL-- alanine, and diglycine (except at lower concentration 1.0 m _B ), negative for L-valine, and both positive and negative for the remaining amino acids over the concentration range studied. The side-chain contributions and hydration numbers have been calculated from V _2,m ^o data. Interaction coefficients have also been obtained from the McMillan–Mayer approach and the data have been interpreted in terms of various interactions.     

Theoretical Description of Excess Molar Functions in the Case of Very Small Excess Values. Investigation of Excess Molar Volumes of Propan-2-ol + Alkanol Mixtures

The densities of propan-2-ol + pentan-1-ol, + hexan-1-ol, + heptan-1-ol, + octan-1-ol + nonan-1-ol and speeds of sound in propan-2-ol + pentan-1-ol, + heptan-1-ol, + nonan-1-ol have been measured over the whole composition range at 298.15 K. Excess molar functions determined from the experimental data have been plotted as functions of composition. The excess molar volumes have been interpreted on the basis of the Symmetrical Extended Real Associated Solution Model (S-ERAS).     

Apparent and Transfer Molar Volumes for Aqueous Solution Containing Polyethylene Glycols and Amino Acid Ionic Liquids at 298.15 K

The densities of 1-n-butyl-3-methylimidazolium ([Bmim]) based amino acid ionic liquids (AAILs) prepared from glycine [Gly], alanine [Ala], and valine [Val], namely [Bmim][Gly], [Bmim][Ala] and [Bmim][Val], in aqueous?~?0.2 mol·kg^?1 polyethylene glycol (PEG400, PEG600 or PEG1000) and PEG400 solutions containing?~?(0.0946, 0.1891 and 0.3820) mol·kg^?1 of [Bmim][Gly], have been determined at 298.15 K. The experimental densities were used to evaluate the apparent molar volumes in the mixed solvent system and further used to obtain transfer molar volumes of AAILs for their transfer from water to aqueous PEG solutions and of PEG400 for its transfer from water to aqueous solutions containing (0.0946, 0.1891 and 0.3820) mol·kg^?1 of [Bmim][Gly]. The transfer molar volumes of AAILs and of PEG400 are found to be negative. The effects of alkyl chain-length variation on the anion of AAILs as well as the chain-length of PEG on transfer molar volumes are investigated and discussed in terms of hydrophobic–hydrophilic, hydrophobic–hydrophobic, and ion–hydrophobic interactions.     

Partial Molar Volumes and Isentropic Compressions of Cyclic Ethers in Aqueous Solutions from 288.15 to 313.15 K at Atmospheric Pressure

The partial molar volumes and isentropic compressions of aqueous solutions of tetrahydrofuran, tetrahydropyran, 1,4-dioxane, tetrahydropyran-2-methanol, 3-hydroxytetrahydrofuran, and tetrahydrofurfuryl alcohol were measured at 288.15, 298.15, and 313.15 K. Results are analyzed in terms of the effects of group addition to the molar volumes and isentropic compressions. The temperature dependence of the molar volumes and compressions, and their group contributions, are used to characterize changes in hydration.     

A Study of Excess Molar Enthalpies and Excess Molar Volumes of Binary Mixtures of 1-Chloropentane + 1-Alkanol (from 1-Butanol to 1-Octanol) at 25°C.

Excess molar enthalpies H ^E _mand excess molar volumes V ^E _m at 25°Cand normal atmospheric pressure for the binary mixtures 1-chloropentane + 1-alkanol(from 1-butanol to 1-octanol) have been determined using a Calvet microcalorimeterand from density measurements using a vibrating tube densimeter. The H ^E _m valuesfor all the mixtures are positive and V ^E _m values are positive or negative dependingon the mole fraction of the chloroalkane. Experimental H ^E _m results are comparedwith the predictions of UNIFAC group-contribution models proposed by Dang andTassios and by Larsen et al., and are discussed in terms of molecular interactions.